feat: Implement BasicAuthManager to support basic authentication

[lishuxu]

feat: Implement BasicAuthManager to support basic authentication

[wgtmac]

Review Report: PR #564

📄 File: src/iceberg/catalog/rest/auth/auth_managers.cc

Java Counterpart: core/src/main/java/org/apache/iceberg/rest/auth/AuthManagers.java and BasicAuthManager.java

• Parity Check: ✅ The C++ logic faithfully implements the Java behavior. It correctly enforces the requirement for basic-username and basic-password properties and properly concatenates them to form the Basic base64-encoded authorization header. The case-insensitive auth-type handling is correctly preserved.
• Style Check: ✅ Uses modern C++ paradigms, including std::string_view, standard containers, and [[maybe_unused]] for ignored parameters. The formatting aligns well with the project's style.
• Logic Check: ✅ Clean logic mapping to Result<T> error handling. No memory leaks or unsafe behaviors detected. Returns an InvalidArgument on missing credentials gracefully rather than throwing raw exceptions.
• Design & Conciseness: ✅ BasicAuthManager is neatly encapsulated within the .cc implementation file, avoiding unnecessary exposure in headers. Reuses existing TransformUtil::Base64Encode rather than rolling a custom base64 encoder.

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📄 File: src/iceberg/test/auth_manager_test.cc

Java Counterpart: Not found (Assumed standard test parity)

• Parity Check: ✅ Comprehensive test coverage corresponding to Java's testing expectations, covering happy paths, case insensitivity, missing properties, and special character edge cases.
• Style Check: ✅ Excellent use of the GTest framework and existing custom matchers (IsOk, IsError, HasErrorMessage).
• Logic Check: ✅ Test logic and base64 assertions are mathematically sound and verifiable.
• Design & Conciseness: ✅ Clean and focused test cases.

Summary & Recommendation

• Approve. The PR is exceptionally clean, mirrors the Java implementation faithfully, respects C++ conventions, and brings good unit test coverage. No blocking issues found.

[wgtmac]

Mostly LGTM. I've left some inline comments. Previous comment was posted by my custom review agent which accidentally approved it.

[wgtmac]

It looks a little bit weird that BasicAuthManager and other AuthManager implementations are declared in auth_managers.h/cc not auth_manager.h/cc. It would be better to move them to the latter and make auth_managers.h/cc simply a factory.

[lishuxu]

Good point!
Moved NoopAuthManager and BasicAuthManager implementations to auth_manager.cc, and added auth_manager_internal.h to expose their factory functions (MakeNoopAuthManager/MakeBasicAuthManager) only to auth_managers.cc.